Braking system for an electrically-operated road such as an escalator

ABSTRACT

In an electrically operated road, such as an escalator, a braking force for stopping the electrically operated road is changed according to whether the running direction is upwardly or downwardly, so that the braking deceleration of the road during emergency stopping of operations will become independent of the running direction of the electrically operated road.

ilnite States Mitsui et a1.

[451 Jul 29, 1975 BRAKING SYSTEM FOR AN ELECTRICALLY-OPERATED ROAD SUCH AS AN ESCALATOR [75] Inventors: Tsuyoshi Mitsui; Takeji lliiramoto;

Mitio llmanaka, all of Katsuta,

Japan [73] Assignee: Hitachi, Ltd., Tokyo, Japan [22] Filed: Oct. 1,1973

[21] Appl. No.: 402,280

1,212,981 Maris ct a1 188/171 1,682,052 8/1928 Radcliffe t 198/232 1,984,801 12/1934 Lindquist ct a1 1 198/232 3,028,934 4/1962- Lister 188/171 3,032,146 5/1962 Szabo Ct 211. 188/171 3,074,517 l/1963 Kohli 188/171 3,160,240 12/1964 Harding, Sr. ct al. 188/171 3,219,155 11/1965 KEihli 188/171 3,298,472 l/l967 Jensen 188/171 3,356,190 12/1967 Prussak 188/171 Primary Examiner-Richard A. Schacher Assistant Examiner Richard K. Thomson Attorney, Agent, or Firm-Thomas E. Beall, Jr.

[5 7] ABSTRACT 23 Claims, 13 Drawing Figures Lunnn u| uunnrrrn PATENTEDJULZQISYB 3,896,925

sum 1 F76. PRIOR ART PATENTEDJULZQISYS sum Fla 3 UPPERLIMITED VALVE LOWER-LIMITED VALVE I I00 MAGNITUDE OF THE LOAD OF THE PASSENGERS BRAKING SYSTEM FOR AN ELECTRICALLY-OPERATED ROAD SUCH AS AN ESCALATOR BACKGROUND OF THE INVENTION The present invention relates systems braking system for an electrically operated road, such as an escalator.

In general, the floor height of an escalator for use at, for example, a transport station having very large facilities, unlike the level difference of the usual department store, office building or the like, will have a level difference between the platforms of the station and the ground that may be well over meters when the urban traffic network is divided into a suitable grid.

In order to relieve crowdedness at the morning and evening rush hours, a high speed escalator has recently been desired.

Additionally, the relationship between passengers riding on upwardly moving escalators and downwardly moving escalators in the morning is quite different than the relationship in the evening. For example, if we assume that in the morning most of the passengers will be riding upwardly on the escalators at a particular station, then it will follow that in the evening most of the passengers will be riding downwardly on this same group of escalators at the station. In this case, some of the escalators that will be operating as upwardly moving escalators in the morning will be switched over to operate as downwardly moving escalators in the evening by merely reversing the direction of escalator running.

If a conventional escalator is subjected to emergency stopping while it is running in the upward direction with a large number of passengers, where will be a great amount of shock to the passengers so that they are most likely to fall down from the sudden stopping of the escalator, because the total weight of the passengers tends to stop the operation of the escalator, that is, the total weight of the passengers will add to the braking force. On the other hand, if this same conventional escalator were operated in the reverse direction to run downwardly, the total weight of the passengers would tend to keep the escalator moving downwardly and be subtracted from the conventional braking force, so that the significance of the emergency stop would be lost and the escalator would not stop sufficiently rapidly. This tendency is increased with a corresponding increase in total height spanned by the escalator and by an increase in the speed of the escalator.

SUMMARY OF THE INVENTION It is accordingly an object of the present invention to overcome the above mentioned disadvantages of the prior art and to provide an emergency braking system suitable for a high speed escalator whose running direction over a great difference in height is changed freroad means will mean a type of conveyor that will in clude both an escalator having steps and a moving road installed for a similar purpose to that of the escalator and having an inclination, but no steps.

When an electrically operated road, such as an escalator, is used to run upwardly, the total passenger weight will tend to increase the braking force for stopping the escalator. Thus, the emergency stopping of a conventional escalator will have a large deceleration that will exceed the limitation imposed by the safety and comfort of the passengers, so that the passengers will not be able to maintain their positions upon emergency stopping. In the present invention, a driving force of the escalator will have a large inertia in order to keep the deceleration of the emergency stop at a suitable value independently of the passenger weight.

On the other hand, if the electrically operated road is used as a downwardly moving road, the large inertia of the driving device will decrease the braking force. The braking system of the present invention has a braking force control means that will change the braking force in accordance with whether the running direction is upwardly or downwardly, in order to keep the deceleration of the electrically operated road at a suitable value for the comfort and safety of the passengers.

A conventional type of escalator has a spring that will apply the braking force. Therefore, it is desirable ac cording to the present invention to change or control this type of spring force for controlling the braking force of the escalator. Although an escalator will be mentioned as a specific example, it is to be understood that as mentioned above, there are other types of devices with which the present invention may be useful, according to the broader aspects of the present disclosure. This spring force may be changed by changing the length or compression or tension of the spring according to the running direction. The spring force of a compression spring that is acting as the brake force may be increased by compressing the spring.

As a further example of the present invention, the braking system may comprise a main spring and an auxiliary spring for causing the braking force. During upward movement of the electrically operated road, only the main spring would be used for causing the braking force, and no auxiliary spring would be used. When the electrically operated road moves in the downward direction, both the main spring and the auxiliary spring would be used for causing the braking force in order to keep the deceleration of the emergency stop at a suitable value independently of the running direction.

Further, it is possible to have a plurality of auxiliary springs. In this case, the braking force can be controlled in response to the number of passengers by changing the number of the effective springs creating the braking force according to the number of passengers that the escalator in carrying in addition to changing the braking force in accordance with the running direction.

BRIEF DESCRIPTION OF THE DRAWING Further objects, features and advantages of the present invention will become more clear from the following detailed description of the drawing, wherein:

FIG. 1 is a schematic view showing a portion of a conventional escalator driving section;

FIG. 2 is a plan view of a portion of a conventional escalator drive taken along line II-II of FIG. 1;

FIG. 3 is a diagram showing a typical relationship between the deceleration of an emergency stop and the passenger load;

FIG. 4 is an enlarged cross sectional view of a part of the braking system according to an embodiment of the present invention;

FIG. 5 is an electric circuit diagram for the braking system of FIG. 4;

FIG. 6 shows a further embodiment of the present invention;

FIG. 7 is an enlarged view of a portion of FIG. 6;

FIG. 8 is a cross sectional view taken along line VIII- VIII of FIG. 6;

FIG. 9 is a sectional view taken along line IXIX of FIG. 6;

FIG. 10 is a side elevation view of the braking system according to FIG. 6;

FIG. .11 is a plan view of a modification of the braking system of FIG. 6;

FIG. 12 is a side elevation view of the braking system according to the modification of FIG. 11; and

FIG. 13 is a control circuit diagram according to another embodiment of the control circuit.

DETAILED DESCRIPTION OF THE PRIOR ART The conventional or prior art type of escalator l as shown in FIG. 1 will transport passengers between an upper floor and a lower floor in such a way that power derived from the electric motor 2 and the transmission 3 will, by means of the endless chain 4, drive the wheel or sprocket 5. This large diameter sprocket 5 is drivingly connected to the slightly smaller diameter sprocket or wheel 6 that is used to in turn drive the endless array of steps 7 that are secured in a conventional manner to the footboard chain 8, which chain 8 is drivingly connected to the sprocket 6. During their endless travel, the steps 7 will travel along and be supported by the rail 9. The escalator may be braked, particularly upon emergency conditions, by means of the brake 10 that is provided at the head of the electric motor 2.

The details of the brake may be seen in FIG. 2, which is a plan view of a portion of FIG. 1 taken along line II- II. As seen in FIG. 2, shoes 14 are provided on right and left hand levers 13. A brake drum 12 is drivingly mounted on the main shaft 11 of the motor 2, to be braked frictionally by the forces of the springs 15 that will tend to move the levers l3 and the shoes 14 carried thereby into radial engagement with the brake drum 12. The shoes 14 are opened, that is moved away from and out of contact with the brake durm, by means of the electromagnet 16 during running of the escalator, by the electromagnet 16 pulling the upper (as seen in FIG. 2) ends of the levers 13 inwardly and by providing the indicated stationary pivots between the points of connection of the electromagnet l6 and the brake shoes 14, so that the levers 13 will be first class levers. When the power source is disconnected, or when otherwise the electromagnet 16 is deenergized, the magnetic force of the electromagnet 16 will effectively disappear and the braking force due to the springs 15 will be exerted on the brake drum 12, as the shoes 14 will pivot inwardly.

In the structure of such a conventional braking system, the pressure of the springs 15 will be set at a predetermined value by means of the indicated lock nuts, and thereafter this value will be constant or unchanged. For this reason, as has been stated previously, especially when the floor height or running height is large and the running speed is quite high, the braking distance and deceleration will be greatly dependent on the direction of running, 05 that the difference between these characteristics for opposite runs will be remarkably high to cause considerable inconvenience and danger to the passengers.

With reference to FIG. 3, the braking deceleration or shock upon emergency stop of the escalator, from the viewpoint of safety and comfort for the passengers, must be limited so as to always have a value within a range from the upper limit S, and the lower limit 8,, independently of the magnitude of the load of the passengers and the direction of running. In the diagram of FIG. 3, the upper limit value S, is the maximum value of the safe braking shock (deceleration) at which the passengers are prevented from experiencing undesirable effects, such as falling. S is the lower limit set for the braking distance, since if the braking distance is very long as would be caused by a small deceleration during emergency stop, the function of the emergency stop would not be effected.

With the braking system of a conventional system wherein the brake force applied would always be constant regardless of running direction, it would be seen that if an emergency stop of the escalator were made under the conditions of a large floor height with passengers, it would be impossible to bring the deceleration or stopping shocks in both directions of ascent and descent within the safe range. More specifically, if the spring force is set so that the braking shock may not become lower than the lower limit value S during descent running, then the shock value becomes a for zero or no passenger load during descent running. With increase in the passenger load, the shock or deceleration value will decrease, that is the braking distance will become longer, as illustrated by the straight line D,. Even at percent load, the deceleration or shock, as determined by lined D,, will not become lower than the lower limit value 8 The braking shock during ascent running, however, will increase with increase in the passenger load as illustrated by the straight line U,. At the load of 100 percent during ascent, it is seen that the shock or deceleration as determined by line U, would be far beyond the upper limit value 8,, and would present a dangerously high braking shock.

On the other hand, if the spring force of the conventional system were set so that the braking shock value or deceleration would not exceed the upper limit value S, even for passenger load of 100 percent during ascent running, the braking shock would be at b under the no load or no passenger condition and increase with increase in load as illustrated by the dot-dash line U and become equal to or lower than the upper limit value S, at 100 percent load. During descent running, the braking distance would become longer as the deceleration would decrease as shown by the line D and for higher loads up to 100 percent, the deceleration would fall far below the lower limit value S so that the purpose of the emergency stop would not be attained.

DETAILED DESCRIPTION OF THE PRESENT INVENTION In view of the above and deficiencies of the conventional system, the present invention has as a purpose and result the maintaining of the shock values or deceleration within the range S, to S for braking during both ascent and descent. The present invention relates not only to escalators but also to electrically moving roads, although the present invention will be described with specific reference to escalators for purposes of the preferred embodiment.

An embodiment of the present invention as shown in FIG. 4 would be used to replace the spring 15 of FIG. 2, for urging the brake shoe levers toward the brake drum of an otherwise conventional escalator as shown in FIG. 1. Accordingly, elements that are common with the conventional system will not be described in detail or shown further in the drawing.

In FIG. 4, the conventional brake lever 13 is urged into braking engagement by the brake spring 15, which brake spring 15 is held at its opposite end by means of a thrust bearing 17 that is provided for transmitting axial forces while allowing rotation between the brake spring seat 18 and a rotatably mounted gear 19. When the servomotor 2,1 is rotated, it will drive a small diameter and elongated pinion 22 for rotation, so that the gear 19 that is meshed therewith will be driven rotatably about its axis and moved in the horizontal direction of the drawing by means of a helical screw thread connection between the gear 19 and the shaft 20 on which it is mounted. Thus, the compression length of the spring 15 may be changed to accordingly change its spring force.

The threaded shaft 20 will extend horizontally through the spring 15, the spring seat 18, the lever 13, and the other elements as indicated. This shaft 20 has a square thread K for providing rotatable threaded interengagement with the gear 19, which acts as a nut, and for preventing rotation between the shaft 20 and spring seat 18. A fitting 23 is rigidly secured to the housing of the motor 21 to be stationary therewith. The shaft 20 is stationarily mounted by means of the fitting 23 and a lock nut 24 that engages an outer machine screw thread T of the shaft 20.

The end of the shaft supporting the pinion 22 that is opposite from the motor 21 is rotatably supported by means of a bearing 25, which is mounted together with the servomotor 21 on the head of the escalator motor 2 as in the prior art brake of FIG. 1.

A bracket 26 is rigidly secured to the spring seat 18 so that it will have only horizontal reciprocating motion as indicated by the arrows along with the spring seat 18. The bracket 26 is provided at one extreme end with a projecting or operating piece 28 that will engage the stationary contacts 31 and 33 of switches 32, 34, respectively. A bracket 30 is provided as shown for mounting the switches 32 and 34 stationarily in spaced relationship, with the bracket 30 having an opening therein for passing the outer end of the rod 20, so that the bracket 30 may be clamped and fixed between the fitting 23 and the lock nut 24.

FIG. 4 illustrates in solid lines the setting of the spring for descent or downward running of the escalator. To reach this state, the gear 19 has been moved rightward as viewed in FIG. 4 by operation of the servomotor 21 to compress the spring 15 to a greater extent than would be provided for upward running. During such adjustment. the operation of the servomotor 21 would continue until the contact 31 of the switch 32 would be depressed by the operating piece 28 to thereby break the circuit for the servomotor and 'prevent further rotation of the gear 19. The amount of compression of the spring 15 can accordingly be easily varied by adjusting the stationary position of the switch 32.

If it is desired to operate the escalator for ascent or upward running after it has been operating in the descent condition as shown in solid lines in FIG. 4, a suitable control which operate the servomotor in the reverse direction so as to move the gear 19 toward the left in FIG. 4. Accordingly, the spring 15 would be increased in length or loosened to reduce its spring force. The gear 19 would be moved leftward into the position indicated by the dot-dash lines at which position the contact 33 of the switch 34 would be depressed by the operating piece 28 to break the circuit to the servomotor and accordingly prevent further movement of the gear 10. Thus, the spring force for the left hand descent position would be less than for the right hand ascent position. Thus, emergency stopping would be safe regardless of whether the escalator were moving upwardly or downwardly, because the spring force would be relatively small for upward movement and relatively large for downward movement.

Both the length of the square thread K by which the gear 19 is fitted onto the rod 20 and the length of the pinion 22 corresponding to the amount of movement of the gear 19 will be determined by the desired braking forces that will be respectively required for the two running directions of the escalator to maintain satisfactory braking conditions.

An interlocking mechanism for the running direction of the escalator and the brake force varying device will now be explained in conjunction with an electric circuit as shown in FIG. 5. When a key switch K is switched on, a main contact A a holding contact A and a control contact A are closed by energization of the coil A. If the switch K for the running direction is switched to the UP side, a coil B is energized to close contacts B B B and B of the circuit for the brake G. As the result, the braking force exerted by the spring is released and the motor 2 will start for the ascent running upon closure of the main contacts B and D Since a contact B is closed to energize a coil Z, a contact Z of the circuit for the servomotor will be closed. If the spring 15 is in the compressed state as shown in FIG. 4, the gear 19 being located at the right hand position of FIG. 4, current for the servomotor 21 will be provided by the sequence of contacts X servomotor 21, contact X contact Z switch 34. Thus, the servomotor 21 will be rotated so as to move the gear 19 in the left hand direction of FIG. 4 so that the contact 31 of the switch 32 will be released as the operating piece 28 is moved leftward out of engagement with the contact 31 so that the switch 32 will be turned on. When the operating piece 28 reaches the contact 33 and engages it, the switch 34 will be turned off to break the circuit to the servomotor 21 and prevent further rotation. Thus, the spring 15 will be loosened to establish a spring setting that will impart the appropriate braking forcefor ascent running.

On the other hand if the spring 15 is in position for ascent running when the escalator is operated in the up direction, the servomotor 21 will not be operated as the circuit is broken by the switch 34. However, if it were then decided to operate the escalator for descent running, the switch K would be moved to the DN" position to energize the coil C for closing of the holding contact C and the control contacts C and C A main contact C would be closed and a contact C of the brake circuit'would be closed to release the brake. Thus, the escalator would be started for descent running. Since the contact C is closed, the coil X will be energized to close contacts X X and X in the circuit of the servomotor 21 and to open the contacts X and X,. As a result, current through the servomotor flows in the opposite direction to that of ascent running, so that the servomotor will operate in the opposite direction of rotation. Therefore, the gear 19 would be moved in the right hand direction for compression of the spring until the switch 32 would be turned off for interrupting flow of current to the servomotor 21. Thus, an appropriate set value for the spring force of the spring 15 would be obtained for descent running.

As described above, in accordance with the present invention, the amount of the compression of the spring 15 can be changed in accordance with the running direction of the escalator. The braking shock or deceleration for emergency stops is thereby made so as to be represented by the straight line U for ascent running and by the straight line D for descent running as has been explained previously with respect to FIG. 3. It is thus seen that the braking shocks during emergency stops will always fall within the allowable range 5, 5-,, which is safe for the passengers, regardless of the load and running direction.

The foregoing is the explanation of one embodiment of the present invention. In summary, the present invention is concerned with an escalator for large floor height or the like structure which changes the spring force of the emergency brake in accordance with the running direction of the escalator to thus provide a variable braking force that will provide braking shocks or deceleration that will be safe to passengers during emergency stopping with respect to both running directions.

In accordance with the present invention, even in the case where the escalator is stopped when it is loaded with a large number of passengers, the braking shock dependent on the running direction thereof can always be restrained to a safe range. In addition, the braking force can also be freely varied in dependence on the magnitude of the floor height by changing the positions of the foregoing switches 32, 34, which may be provided with adjustable mountings on the bracket 30. It is therefore possible to always keep the shock for the passengers within the safe range during emergency stops.

Another embodiment of the present invention is shown in FIGS. 6, 7, 8, 9, 10, 11, and 12. Only those portions that differ from the foregoing embodiment will be described in detail and it is readily apparent how the structure of the second embodiment may be employed with the otherwise conventional escalator of FIGS. 1 and 2.

As shown in FIG. 6, a brake drum 612 is fixedly secured on the main shaft 611 of the motor and is frictionally braked by the application of shoes 614 that are mounted on right and left hand levers 616 and 618, respectively. To one side of the shoes, the levers are pivotally mounted to each other and to the other side of the shoes the levers are secured to a main magnetic coil 630 and an auxiliary magnetic coil 632. Each of these coils has moving portions 620, 622 which are attracted or moved by energization of each coil and which will thereby open the levers 616, 618 against the force of springs 624, 626 so as to separate the shoes 614 from the drum 612. A rod 628 extends through a hole that is provided in the centers of the moving portions 620, 622 of the auxiliary coil 632, as shown in more detail in FIG. 7, and two holes of each left end of the levers 616, 618. The upper end of the rod 628 is provided with a spring 626, one end of which engages a stop 634 secured to the shaft 628 by a nut, and the other end of which engages a cross piece 636 that is mounted on bolts 640, 642, which bolts are fixedly mounted at their opposite ends to a cross plate 644. The plate 644 is mounted by push bolts 646, 648, which have their opposite ends fixedly mounted in the moving portion 620 of the auxiliary coil and which bolts 646, 648 further extend through holes within moving portion 622.

An enlarged portion of FIG. 6 that is enclosed by the dot-dash circle 700 is shown in more detail in FIG. 7. The rod 628 is provided movably on the lever 616. The moving portion 622 is movably supported in the rod 628 by means of an enlarged hole 710 therein and further is provided with two holes 712, 714 through which the push bolts 648 and 646 respectively extend to where they are secured to the moving portion 620. The other ends of the push bolts 646, 648 are positioned through the holes of the plate 644, respectively. Springs 716, 718 are respectively provided between the plate 644 and the moving portion 622 surrounding the bolts so as to move the plate independently of the upper ends of these bolts 646, 648. The plate 644 has the two bolts 640, 642 rigidly secured thereto on which the sheet 636 is secured by scress formed on the ends of the bolts 642, 640 and in the sheet 636. The coil spring 626 is provided between the stop 634 of the shaft 628 and the cross piece 636.

FIG. 8 is a cross sectional view on line VII-VIII of FIG. 6. The electromagnetic coil 632 has the moving portion 620 provided with three holes 810, 812, 814 through which pass the bolt 628 and the two push bolts 846 and 848. The lower ends of the push bolts 646, 648 are received and secured by the moving portion 620 adn the upper ends of the push bolts 646, 648 are received and secured within the moving portion 622 (not shown).

FIG. 9 is a cross sectional view taken along line IX-IX of FIG. 6. The moving portion 620 is provided with two holes 814, 812 through which the push bolts 846, 848 extend. The lower ends of the push bolts 846, 848 are engaged with the cross piece 934 by the springs 916, 918. The two bolts 940, 942 are rigidly secured to the cross piece 934 and have a cross piece 936 with two negative screw holes cooperating withthe screws of the holes 940, 942.

With reference to FIGS. 6, 7, 8, 9, when the coil 632 is energized, the moving portions 620, 622 of the auxiliary coil 630 are attracted to each other so that the push bolts 646, 648 fixed on the moving portion 620 and the push bolts 846, 848 fixed on the moving portion 622 are pushed toward the outside. This movement of the push bolts will push the cross pieces 636, 936 and cause the gaps G between the spring cross piece 636 and the lever 616 and between the spring cross piece 936 and the lever 618 against the force of the spring 626. If the electromagnetic coil 632 is disconnected, that is deenergized, the force of the spring 626 will be applied to the levers 616, 618 through the spring cross pieces 636, 936 so as to cause frictional engagment between the shoes 614 and the drum 612.

When the electrically operated road or escalator is driven so as to be moving upwardly or in the ascent stage. the total weight of the passengers will have a tendency to stop the escalator. Only the magnetic coil 630 will be disconnected, in order to keep the value of the deceleration of an emergency stop at a suitable value.

On the other hand, during downward running, the weight of the passengers will have a tendency to keep the escalator moving in the downward direction. Thus, both the main coil 630 and the auxiliary coil 632 will be disconnected or deenergized for increasing the friction between the shoes and the drum. As a result, the value of the deceleration of the escalator for an emergency stop will be independent of the running direction.

Each of the spring cross pieces 636, 936 has a projection which engages each recess of the left ends of levers 616, 618 in order to prevent a shifting of the mechanism.

A side view of the braking device as shown in FIGS. 6, 7, 8, 9 is illustrated in FIG. 10. In FIG. 10, the motor 2 is provided with the transmission 3. The levers 616, 618 (only one of which is shown) will have the brake shoes 614 shown previously and will be movably supported by means of member 1050, which acts as a fulcrum for the levers. The mgnetic coils 632, 630 will operate to close the levers and stop rotation of the drum 612.

A further embodiment of the present invention is shown in FIGS. 11 and 12, wherein the force of the spring 1124 is applied to levers 1116, 1118 having shoes 1114 to apply braking friction to the brake drum 1112. The electromagnetic coil 1130 causes compression of the spring 1124 and opens the levers 1116, 1118. Particularly, the push bolts 1140 fixed on the moving portion 1120 and the push bolts 1142 fixed on the moving portion 1122 will push the levers 1116, l 1 l8 outwardly away from each other upon movement of the moving portions inwardly upon energization of the coil 1130. The levers are pivotally supported on cross member 1150.

When the electromagnetic coil 1130 is disconnected, the force of spring 1124 is applied to the levers 1116, l 1 18 for stopping of the drum 1112. If it is needed to increase the braking force, the auxiliary electromagnetic coil 1132 is also disconnected, so that the forces of springs 1160, 1162 will be applied to the levers 1116, 1118 through the two push bolts 1146, 1148 to further increase the braking force. When the coil 1132 is energized, the two moving portions 1123, 1121 are attracted toward each other and the bolts 1146 and 1148 will move against the bias of the spring 1160, 1162 so that gaps G will be formed between the bolt ends and the right hand ends of the levers 1116, 1118.

With reference to FIG. 13, the motor 2 is connected to a voltage supply through contacts B or C and D At first, an escalator is inspected and the safety switch K, is turned on when there in no accident.

When a key switch K is turned on in addition, contacts A,, A are switched on by energizing the coil A. The energizing current is held by connection of the contact A, even after the key switch K is opened.

If a switch K, for the running direction is switched to the UP side, the coil B will be energized for closing contacts B,,, B,, B,, B,, B B and for opening contact 3,. The closing of the contact B, holds the current for energizing the coil B after switch K is turned off. The disconnection of the contact B will disconnect a coil C from the voltage supply. If the switch K is switched to the DN side during the ascent running by a mistake of the operator, the coil C cannot be energized.

When the contact 13;, is closed, a timer relay TE is energized for closing the contact TE,; this timer relay has a certain delay time for thereafter disconnecting the contact TE,. If the timer relay TE is disconnected from the voltage supply by turning off or opening the contact 3;, after a certain period of time the contact TE, is disconnected. The connection of the contact 8., energizes a coil F which connects the contact F,. Since the contact TE, has been connected by energizing the timer relay TE, the current into the coil F also flows through the contacts TE,, F,. If the contact 8., becomes disconnected, all current for the coil F flows through the contacts TE,, F, until the contact TE, is disconnected. The operation of the contacts F,, F, has a delay time defined by the delay time relay TE. The coil H is energized by a connection of the contact F and a contact H, for magnetic coil 18 of the auxiliary brake is thereby connected for energization. As a result, the force of the spring 624 (1124) of FIG. 6 (11) cannot be applied on the levers 616 (1116), 618 (1118), and cannot work as a power for the brake.

A coil I having contacts 1,, J, is energized by a connection of the contacts L,, B,,, with the contact L, being switched on when the coil L is not energized, and the contact 3, being switched on by energization of the coil B. A coil 630 (1130) is energized by closing of the contact J and the levers 616 (1116), 618 (1118) are expanded against the force of the spring 624 (1124) so that gaps between the shoes 614 (1114) and the drum 612 (1112) are created. The contact D is turned on by energization of coil D due to the switching on of the contact B The electric power that is applied to the motor 2 is supplied through contacts C B D If an emergency occurs suddenly, the switch K, is turned off. The contacts A,, A, will thereby be turned off by denergization of the coil A. The contacts B B,, B,, B,,, B B,, will accordingly be turned off by deenergization of the coil B. Thus, the coils J, D, will be deenergized, and the contacts D J willbe turned off. The motor 2 will be disconnected from the power supply by opening of the contacts B D The magnetic coil 630 (1130) will also be disconnected from the power supply which comprises a rectifier circuit 1350 having four diodes and a AC. voltage supply. The force of the spring 624 (1124) of FIG. 6 (11) will be applied to the levers 616 (1116), 618 (1118) for braking of the drum 612 (1112). The timer relay TE has a certain delayed time, which is the period between the time when the time relay is disconnected from the power supply by disconnecting the contact B, and the time when the contact TE, of the timer relay TE is turned off. Therefore, despite the fact that the contact B,, is disconnected, since the contact TE, is switched on for certain periods determined by the delay time of the timer relay TE, the coil F is energized for this period until the contact TE, is turned off. After the switch K, under emergency conditions is turned off, the coil H is energized for the certain period of the timer relay and the switch H, is kept closed for this predetermined period of time. Thus, the coil 632 (1132) for the auxiliary brake is energized for the predetermined period of time as determined by the delay time after the switch K, under emergency conditions is turned off, so that for that predetermined period of time of the timer relay TE, the auxiliary brake will not work.

On the other hand, the coil vJ having the contact J, is disconnected from the power supply by turning off the contact 8, at almost the same time as the emergency switch K is turned off. Since the coil 630 (1130) of the main brake is disconnected from the power supply at the same time, the main brake works as soon as the switch K is turned off. i

As explained above, in the case of ascent, the main brake is engaged at first and after a predetermined period of time, the auxiliary brake will be engaged. During ascent running, the weight of the passengers will act in the direction against the running direction, so that only the main brake will act as the brake force for the escalator. When the movement of the escalator stops, the weight of the passengers acts on the escalator, tending to cause a movement of the escalator downward. It is desirable to then engage the auxiliary brake in order to prevent such downward movement or slipping of the escalator, after the escalator has been stopped by the main brake. It is desirable that the delay time of the timer relay TE be the same as the period that is needed to stop the escalator. Referring to FIG. 6 or FIG. 11, when the emergency switch K is turned off, the coil 630 (1130) is disconnected first, and the force of the spring 624 is applied on the drum 612 through the levers 618, 616 and shoes 614. Thereafter, the coil 632 (1132) is disconnected from the power supply and the force of the spring 626 (1160), 1162 is also applied on the drum 12 after the drum 12 is stopped for preventing the slipping movement being caused by the weight of the passengers after the escalator has stopped.

Assuming that operation of the escalator is in the descent running condition, that is with switches K K being turned on and the switch is turned toward the down side, the coil C is energized and the contacts C C C C C are turned on. The coils 630 (1130), 632 (1132) are energized by switching on the contacts L H respectively. The shoes 14 of FIG. 6 (11) will separate from the surface of the drum 612 (1112).

If an emergency condition occurs, the emergency switch K, is turned off. The coil C is disconnected by opening of the contact A and the contacts C C C are switched off. The coils H, L become deenergized and the contacts H J are disconnected, which in turn will deenergize the coils 630 (1130), 632 (1132) at the same time. The forces of the spring 624, 626 (1124, 1160, 1162) are simultaneously applied on the drum 612 (11 12) for stopping the movement of the escalator through the levers 616 (1116), 618 (1118) and the shoe 614 (1114).

When the escalator is in the descent running condition, the forces of the springs 624, 626 (1124, 1160, 1 162) are simultaneously applied on the drum for stopping the movement of the escalator.

On the other hand when the escalator is in the ascent running condition, the main braking means having the coil 630 (1130) and the spring 624 (1124) will work at first for stopping the escalator and then the auxiliary braking means having the coil 632 (1132) and spring 626 (1160, 1162) will work for applying the force of the springs on the drum 612 (1112) through the shoe 614 (1114) as a braking force upon emergency conditions.

Since the operation of the various embodiments, with modifications has been set forth during the description of the structure, further details of the operation are unnecessary.

While various embodiments, modifications and variations have been set forth in purposes of illustration and for the advantageous details in their own right, further embodiments, modifications, and variations are contemplated according to the broader aspects of the present invention, all as determined by the spirit and scope of the following claims.

What is claimed is:

1. A braking system for a power-operated road means for transporting passengers along a vertical component of running, comprising: first means for producing a running direction signal correlated to the running direction of said power-operated road means; emergency switching means for automatically generating an emergency signal when an emergency condition occurs when said road means should be secured against movement; braking means for generating braking force acting to stop said power-operated road means in response to said emergency signal from said emergency switching means; and said braking means including brake force control means, providing an ascent braking force in response to the running direction signal from said first means indicating an ascent road running and providing a descent braking force substantially greater than said ascent braking force in response to the running direction signal from said first means indicating a descent road running.

2. A braking system for the road means in accordance with claim 1, wherein said braking means has at least one auxiliary braking means and a main braking means; and said braking force control means operates only said main braking means in response to said first means indicating an ascent road running, and operates both said main and auxiliary braking means in response to said first means indicating a descent road running.

3. A braking system for the road means in accordance with claim 1, including a prime mover for driving the power-operated road; said braking means including a rotatably mounted drum drivingly connected to said prime mover, brake shoe means mounted for movement into and out of engagement with said drum for producing the braking force, lever means having a first closed position holding said brake shoes in engagement with said drum to produce the braking force and having a second opened position holding said brake shoes out of frictional engagement with said drum, spring means biasing said lever means into its closed position, electromagnetic means for producing a-force upon said lever means in opposition to said spring bias to move said lever means from its closed position to its opened position against said spring bias, and second switching means for selectively energizing said electromagnetic means when there is no emergency signal being produced by said emergency switching means and for deenergizing said electromagnetic means in response to an emergency signal from said emergency switching means; and said braking force control means changing the force supplied by said spring means automatically in response to the running direction signal produced by said first means.

4. A braking system for the road means in accordance with claim 3, wherein said spring means includes at least one spring having opposite ends respectively acting between a reference portion and said lever means, and said braking force control means automatically changing the position of the reference portion in response to said running direction signal.

5. A braking system for the road means in accordance with claim 3, wherein said spring means includes a main spring acting upon said lever means and at least one auxiliary spring acting upon said lever means, and said braking force control means applying a lesser number of springs to act upon said lever means during ascent that are applied during descent.

6. A braking system for the road means in accordance with claim 5, wherein said power-operated road means is an escalator, said prime mover is an electric motor, including power switching means selectively connecting said electric motor to a power supply for running said electric motor in opposite directions.

7. A braking system for the road means in accordance with claim 1, wherein said braking force control means includes an electric delay circuit for automatically delaying a predetermined period of time after the application of the ascent braking force during ascent running sufficiently for stopping the road and immediately thereafter increasing the braking force to resist downward slipping of the stopped road means under load.

8. A braking system for the road in accordance with claim 1, wherein said braking means includes a spring for producing the braking force and electromagnetic means for preventing the application of the spring braking force; and said braking control means changes the force of said spring according to the running direction.

9. A braking system for the road means in accordance with claim 8, wherein said braking means includes a brake shoe and a lever extending between one end of said spring and said brake shoe; and said braking force control means including reference abutment engaging the opposite end of said spring, a stationarily mounted threaded shaft, a nut threadably engaged and rotatably mounted on said shaft in abutting axial engagement with said reference abutment, a reversible electric motor, and a gear drivingly connected to said reversible electric motor and in inter-meshing engagement with said nut.

10. A braking system for the road means in accordance with claim 1, wherein said braking means includes a brake shoe, a pivotally mounted lever means for engaging said brake shoe, spring means for applying a spring bias to said lever means in the direction for applying the braking force and further for producing the braking force, and first and second electromagnetic means, each for engaging said lever means and for moving said lever means against said spring bias out of braking shoe engagement when energized; said braking force control means deenergizing only one of said electromagnetic means under emergency conditions in the ascent running direction and deenergizing both of said electromagnetic means under emergency conditions in the descent direction.

11. A braking system for the road means in accordance with claim 1, wherein said braking means includes a brake shoe, a pivotally mounted lever means for engaging said brake shoe, spring means for applying a spring bias to said lever means in the direction for applying the braking force and further for producing the braking force, and electromagentic means having two axially aligned movable core portions within one magnetic field producing means; said electromagnetic means having first tie rod means attached to one of said portions, extending through the other of said portions and being drivingly connected to one end of said spring means, and second tie rod means attached to the other of said portions, extending through said one portion and being drivingly connected to the other end of said spring means.

12. A braking system for the road means in accordance with claim 1, including a prime mover for driving the power-operated road means and braking means including a rotatably mounted member drivingly connected to said prime mover for rotation with running of said power-operated road means, brake shoe means mounted for movement into and out of engagement with said rotatable member for producing the braking force, first spring means biasing said brake shoe means toward said rotatably mounted member; first electromagnetic means for holding said brake shoe means out of engagement with said rotatably mounted member against the bias of said first spring means when energized, and when not energized permitting said first spring means to move said brake shoe means into engagement with said rotatably mounted member; second spring means for biasing said brake shoe means into engagement with said rotatably mounted member to produce a braking force in addition to the braking force produced by said first spring means biasing said brake shoe means into engagement with said rotatably mounted member; second electromagnetic means preventing the application of the spring bias of said second spring means to said brake shoe means when energized and permitting the application of the spring bias of said second spring means in the direction of engagement of said brake shoe means and said rotatably mounted m'ember when deenergized; and said braking force control means normally energizing both of said first and second electromagnetic means in the absence of an emergency signal, deenergizing said first electromagnetic means and maintaining said second electromagnetic means energized in response to an emergency signal from said emergency switching means and a running direction signal from said! first means indicating an ascent road running, and deenergizing both of said first and second electromagentic means in response to an emergency signal from said emergency switching means and a running direction signal from said first means indicating a descent road running, so that only the bias of said first spring means is applied to produce the braking force between said braking shoe means and rotatably mounted member under emergency conditions during ascent and further so that the spring bias of both said first and second spring means is applied to produce a correspondingly larger braking force between said brake shoe means and said rotatably mounted member under emergency conditions during descent.

13. A braking system for the road means in accordance with claim 12, wherein said braking force control means includes an electric delay circuit for automatically delaying a predetermined period of time after the application of the ascent braking force during ascent running sufficiently for stopping the poweroperated road means and immediately thereafter deenergizing both said first and second electromagnetic means for applying the spring bias of both said first and second spring means under emergency conditions to resist downward slipping of the emergency stopped poweroperated road means under load.

14. A braking system for the road means in accordance with claim 12, wherein said brake shoe means includes a brake shoe drivingly connected to a pivotally mounted lever mounted for movement between an opened position out of engagement with said rotatably mounted member and a closed position in engagement with said rotatably mounted member; said first spring means directly engaging said lever to bias it towards said rotatably mounted member in both said opened and closed positions; said first electromagnetic means directly engaging said lever to move it from its closed position to its opened position when energized against the bias of said first spring means; said second electromagnetic means holding said second spring means out of engagement with said lever in both said opened position and closed position when energized and applying the spring bias of said second spring means only when deenergized by permitting engagement of said second spring means with said lever in both said opened and closed positions.

15. A braking system for the road means in accordance with claim 12, wherein said brake shoe means includes two brake shoes engaging opposite sides of said rotatably mounted member, two levers drivingly connected respectively to said two brake shoes and being pivotally mounted for movement between opened and closed positions; and wherein said first spring means engages between said levers to simultaneously bias them towards their closed position, said first electromagnetic means engages between said levers to simultaneously drive them from their closed position to their opened position against the bias of said first spring means, and said second spring means and second electromagnetic means applying the bias of said second spring means simultaneously to said levers when said second electromagnetic means is deenergized and completely removing the bias of said second spring means when said second electromagnetic means is energized in both of said opened and closed positions.

16. A braking system for the road means in accordance with claim 15, wherein said braking force control means includes an electric delay circuit for automatically delaying a predetermined period of time after the application of the ascent braking force during ascent running sufficiently for stopping the poweroperated road means and immediately thereafter deenergizing both said first and second electromagnetic means for applying the spring bias of both said first and second spring means under emergency conditions to resist downward slipping of the emergency stopped power-operated road means under load.

17. A braking system for the road means in accordance with claim 15, wherein said levers are pivotally connected together, said brake shoes and at least one of said first and second spring means and at least one of said first and second electromagnetic means are mounted on the same side of the pivots of said levers.

18. A braking system for the road means in accordance with claim 17, wherein the other of said spring means and the other of said electromagnetic means are mounted on the same side of the lever pivots as said brake shoes.

19. A braking system for the road means in accordance with claim 17, wherein the other of said spring means and the other of said electromagnetic means are mounted on the opposite side of the lever pivots from said brake shoes.

20. A braking system for the road means in accordance with claim 17, wherein the pivotal connection between said levers is provided by link means pivotally connected at one end to one of said levers and at its opposite end to the other of said levers; said first spring means comprising a rod on the opposite side of said rotatably mounted member from said link means and being secured at one end to one of said levers and having a spring abutment at its opposite end, and a compression spring between said spring abutment and the other of said levers; said first electromagnetic means having a single electromagnetic coil, a first core member movably mounted within said coil and drivingly connected to one of said levers and a second core member movably mounted within said coil and drivingly connected to the other of said levers; said electromagnetic coil being mounted between said levers on the same side of said rotatably mounted member as said first spring means; the driving connection between each of said movably mounted core members and its respective lever comprising at least one rigid rod fixedly connected at one end to its respective core member, fixedly connected at its opposite end to its respective lever and intermediate said ends extending through the other of said core members.

21. A braking system for the road means in accordance with claim 20, wherein said second spring means is a coil compression spring, and wherein said second electromagnetic means includes an electromagnetic coil, two separate core members movably mounted with respect to each other and with respect to said coil and being mounted within said coil for axial movement in the axial direction of said coil spring, a rod drivingly connected at one end to one of said core members and at its opposite end to one end of said coil spring for compressing said coil spring upon movement of the core members into said coil upon energization of said coil; said core members and coil being positioned between said levers.

22. A braking system for the road means in accordance with claim 21, wherein said second electromagnetic means includes a second rod drivingly connected at one end to the other of said core members and at its opposite end to the other end of said coil spring for further compressing said coil spring when said other core member moves into said coil upon energizing the coil.

23. A braking system for the road means in accordance with claim 21, wherein said second electromagnetic means includes a second coil compression spring on the opposite side of said coil and core members from said first mentioned coil spring, and a second rod drivingly connected at one end to the other of said core members and drivingly connected at its opposite end to the second coil spring; means drivingly connecting the ends of both of said coil springs opposite from their connection with their respective rods to the opposite axial ends, respectively, of said electromagnetic coil. 

1. A braking system for a power-operated road means for transporting passengers along a vertical component of running, comprising: first means for producing a running direction signal correlated to the running direction of said power-operated road means; emergency switching means for automatically generating an emergency signal when an emergency condition occurs when said road means should be secured against movement; braking means for generating braking force acting to stop said power-operated road means in response to said emergency signal from said emergency switching means; and said braking means including brake force control means, providing an ascent braking force in response to the running direction signal from said first means indicating an ascent road running and providing a descent braking force substantially greater than said ascent braking force in response to the running direction signal from said first means indicating a descent road running.
 2. A braking system for the road means in accordance with claim 1, wherein said braking means has at least one auxiliary braking means and a main braking means; and said braking force control means operates only said main braking means in response to said first means indicating an ascent road running, and operates both said main and auxiliary braking means in response to said first means indicating a descent road running.
 3. A braking system for the road means in accordance with claim 1, including a prime mover for driving the power-operated road; said braking means including a rotatably mounted drum drivingly connected to said prime mover, brake shoe means mounted for movement into and out of engagement with said drum for producing the braking force, lever means having a first closed position holding said brake shoes in engagement with said drum to produce the braking force and having a second opened position holding said brake shoes out of frictional engagement with said drum, spring means biasing said lever means into its closed position, electromagnetic means for producing a force upon said lever means in opposition to said spring bias to move said lever means from its closed position to its opened position against said spring bias, and second switching means for selectively energizing said electromagnetic means when there is no emergency signal being produced by said emergency switching means and for deenergizing said electromagnetic means in response to an emergency signal from said emergency switching means; and said braking force control means changing the force supplied by said spring means automatically in response to the running direction signal produced by said first means.
 4. A braking system for the road means in accordance with claim 3, wherein said spring means includes at least one spring having opposite ends respectively acting between a reference portion and said lever means, and said braking force control means automatically changing the position of the reference portion in response to said running direction signal.
 5. A braking system for the road means in accordance with claim 3, wherein said spring means includes a main spring acting upon said lever means and at least one auxiliary spring acting upon said lever means, and said braking force control means applying a lesser number of springs to act upon said lever means during ascent that are applied during desceNt.
 6. A braking system for the road means in accordance with claim 5, wherein said power-operated road means is an escalator, said prime mover is an electric motor, including power switching means selectively connecting said electric motor to a power supply for running said electric motor in opposite directions.
 7. A braking system for the road means in accordance with claim 1, wherein said braking force control means includes an electric delay circuit for automatically delaying a predetermined period of time after the application of the ascent braking force during ascent running sufficiently for stopping the road and immediately thereafter increasing the braking force to resist downward slipping of the stopped road means under load.
 8. A braking system for the road in accordance with claim 1, wherein said braking means includes a spring for producing the braking force and electromagnetic means for preventing the application of the spring braking force; and said braking control means changes the force of said spring according to the running direction.
 9. A braking system for the road means in accordance with claim 8, wherein said braking means includes a brake shoe and a lever extending between one end of said spring and said brake shoe; and said braking force control means including reference abutment engaging the opposite end of said spring, a stationarily mounted threaded shaft, a nut threadably engaged and rotatably mounted on said shaft in abutting axial engagement with said reference abutment, a reversible electric motor, and a gear drivingly connected to said reversible electric motor and in inter-meshing engagement with said nut.
 10. A braking system for the road means in accordance with claim 1, wherein said braking means includes a brake shoe, a pivotally mounted lever means for engaging said brake shoe, spring means for applying a spring bias to said lever means in the direction for applying the braking force and further for producing the braking force, and first and second electromagnetic means, each for engaging said lever means and for moving said lever means against said spring bias out of braking shoe engagement when energized; said braking force control means deenergizing only one of said electromagnetic means under emergency conditions in the ascent running direction and deenergizing both of said electromagnetic means under emergency conditions in the descent direction.
 11. A braking system for the road means in accordance with claim 1, wherein said braking means includes a brake shoe, a pivotally mounted lever means for engaging said brake shoe, spring means for applying a spring bias to said lever means in the direction for applying the braking force and further for producing the braking force, and electromagentic means having two axially aligned movable core portions within one magnetic field producing means; said electromagnetic means having first tie rod means attached to one of said portions, extending through the other of said portions and being drivingly connected to one end of said spring means, and second tie rod means attached to the other of said portions, extending through said one portion and being drivingly connected to the other end of said spring means.
 12. A braking system for the road means in accordance with claim 1, including a prime mover for driving the power-operated road means and braking means including a rotatably mounted member drivingly connected to said prime mover for rotation with running of said power-operated road means, brake shoe means mounted for movement into and out of engagement with said rotatable member for producing the braking force, first spring means biasing said brake shoe means toward said rotatably mounted member; first electromagnetic means for holding said brake shoe means out of engagement with said rotatably mounted member against the bias of said first spring means when energized, and when not energized permitting said first spring means to move said brake shoe means into engAgement with said rotatably mounted member; second spring means for biasing said brake shoe means into engagement with said rotatably mounted member to produce a braking force in addition to the braking force produced by said first spring means biasing said brake shoe means into engagement with said rotatably mounted member; second electromagnetic means preventing the application of the spring bias of said second spring means to said brake shoe means when energized and permitting the application of the spring bias of said second spring means in the direction of engagement of said brake shoe means and said rotatably mounted member when deenergized; and said braking force control means normally energizing both of said first and second electromagnetic means in the absence of an emergency signal, deenergizing said first electromagnetic means and maintaining said second electromagnetic means energized in response to an emergency signal from said emergency switching means and a running direction signal from said first means indicating an ascent road running, and deenergizing both of said first and second electromagentic means in response to an emergency signal from said emergency switching means and a running direction signal from said first means indicating a descent road running, so that only the bias of said first spring means is applied to produce the braking force between said braking shoe means and rotatably mounted member under emergency conditions during ascent and further so that the spring bias of both said first and second spring means is applied to produce a correspondingly larger braking force between said brake shoe means and said rotatably mounted member under emergency conditions during descent.
 13. A braking system for the road means in accordance with claim 12, wherein said braking force control means includes an electric delay circuit for automatically delaying a predetermined period of time after the application of the ascent braking force during ascent running sufficiently for stopping the power-operated road means and immediately thereafter deenergizing both said first and second electromagnetic means for applying the spring bias of both said first and second spring means under emergency conditions to resist downward slipping of the emergency stopped power-operated road means under load.
 14. A braking system for the road means in accordance with claim 12, wherein said brake shoe means includes a brake shoe drivingly connected to a pivotally mounted lever mounted for movement between an opened position out of engagement with said rotatably mounted member and a closed position in engagement with said rotatably mounted member; said first spring means directly engaging said lever to bias it towards said rotatably mounted member in both said opened and closed positions; said first electromagnetic means directly engaging said lever to move it from its closed position to its opened position when energized against the bias of said first spring means; said second electromagnetic means holding said second spring means out of engagement with said lever in both said opened position and closed position when energized and applying the spring bias of said second spring means only when deenergized by permitting engagement of said second spring means with said lever in both said opened and closed positions.
 15. A braking system for the road means in accordance with claim 12, wherein said brake shoe means includes two brake shoes engaging opposite sides of said rotatably mounted member, two levers drivingly connected respectively to said two brake shoes and being pivotally mounted for movement between opened and closed positions; and wherein said first spring means engages between said levers to simultaneously bias them towards their closed position, said first electromagnetic means engages between said levers to simultaneously drive them from their closed position to their opened position against the bias of said first spring means, and said second spring means and second eLectromagnetic means applying the bias of said second spring means simultaneously to said levers when said second electromagnetic means is deenergized and completely removing the bias of said second spring means when said second electromagnetic means is energized in both of said opened and closed positions.
 16. A braking system for the road means in accordance with claim 15, wherein said braking force control means includes an electric delay circuit for automatically delaying a predetermined period of time after the application of the ascent braking force during ascent running sufficiently for stopping the power-operated road means and immediately thereafter deenergizing both said first and second electromagnetic means for applying the spring bias of both said first and second spring means under emergency conditions to resist downward slipping of the emergency stopped power-operated road means under load.
 17. A braking system for the road means in accordance with claim 15, wherein said levers are pivotally connected together, said brake shoes and at least one of said first and second spring means and at least one of said first and second electromagnetic means are mounted on the same side of the pivots of said levers.
 18. A braking system for the road means in accordance with claim 17, wherein the other of said spring means and the other of said electromagnetic means are mounted on the same side of the lever pivots as said brake shoes.
 19. A braking system for the road means in accordance with claim 17, wherein the other of said spring means and the other of said electromagnetic means are mounted on the opposite side of the lever pivots from said brake shoes.
 20. A braking system for the road means in accordance with claim 17, wherein the pivotal connection between said levers is provided by link means pivotally connected at one end to one of said levers and at its opposite end to the other of said levers; said first spring means comprising a rod on the opposite side of said rotatably mounted member from said link means and being secured at one end to one of said levers and having a spring abutment at its opposite end, and a compression spring between said spring abutment and the other of said levers; said first electromagnetic means having a single electromagnetic coil, a first core member movably mounted within said coil and drivingly connected to one of said levers and a second core member movably mounted within said coil and drivingly connected to the other of said levers; said electromagnetic coil being mounted between said levers on the same side of said rotatably mounted member as said first spring means; the driving connection between each of said movably mounted core members and its respective lever comprising at least one rigid rod fixedly connected at one end to its respective core member, fixedly connected at its opposite end to its respective lever and intermediate said ends extending through the other of said core members.
 21. A braking system for the road means in accordance with claim 20, wherein said second spring means is a coil compression spring, and wherein said second electromagnetic means includes an electromagnetic coil, two separate core members movably mounted with respect to each other and with respect to said coil and being mounted within said coil for axial movement in the axial direction of said coil spring, a rod drivingly connected at one end to one of said core members and at its opposite end to one end of said coil spring for compressing said coil spring upon movement of the core members into said coil upon energization of said coil; said core members and coil being positioned between said levers.
 22. A braking system for the road means in accordance with claim 21, wherein said second electromagnetic means includes a second rod drivingly connected at one end to the other of said core members and at its opposite end to the other end of said coil spring for further compressing said coil spring when said other core member moves intO said coil upon energizing the coil.
 23. A braking system for the road means in accordance with claim 21, wherein said second electromagnetic means includes a second coil compression spring on the opposite side of said coil and core members from said first mentioned coil spring, and a second rod drivingly connected at one end to the other of said core members and drivingly connected at its opposite end to the second coil spring; means drivingly connecting the ends of both of said coil springs opposite from their connection with their respective rods to the opposite axial ends, respectively, of said electromagnetic coil. 